1. Field of the Invention
The invention relates to a device and a method for automatically connecting two workpieces by means of fasteners, said device having a magazine for receiving the fasteners.
2. The Prior Art
Devices of this kind are used in motor-vehicle production, for example during “marriage” operations involving the bolting together of body and chassis. The invention is described below on the basis of this typical application, to which, however, it is not restricted. On the contrary, it may be used in all areas in which two workpieces are joined automatically by means of fasteners.
For bolting purposes, it is familiar practice to use extension spindles in a bolting station. The bolts are inserted into the extension spindles in advance by workers while setting up the equipment. This procedure, however, necessitates providing pallets with an extension spindle for every bolting point, incurring high pallet costs. The total number of extension spindles increases with the number of pallets in the marriage system, in turn pushing up the cost of the overall system. With mixed-type operations involving the use of different bolts, the complexity of the pallets increases. This increase in pallet complexity may, in turn, necessitate use of a pallet-switching system with conveying and pallet storage means. An additional vehicle type also necessitates new pallets, which incurs costs and is time-consuming.
According to alternative prior art, workers setting up the equipment screw the bolts into a stationary “pallet nest” provided with threaded holes. In the bolting station, a robotic tool unscrews the bolts one after the other and inserts them into the body. Here too, workers setting up the equipment have to screw the bolts into the pallet nest, a repetitive task which is also relatively time-consuming. Moreover, the robotic tool then has to unscrew the bolts again from the pallet nest, requiring a certain degree of cycle time.